1. Field of the Invention
The present invention relates to an image forming apparatus, and may be an inkjet printer, a facsimile machine, a laser printer, etc., and more particularly, to a pulley fixing apparatus of an image forming apparatus, which can easily mount and dismount a power-transmitting belt and a driven pulley, and easily control a tension of the power-transmitting belt.
2. Description of the Related Art
Generally, an image forming apparatus, for example an inkjet printer 1, has a carrier 20 mounting a print head 30 having a nozzle for jetting ink, a chassis 10 having side frames 12 and 12′ to support a guide rail 11 and a carrier shaft 50 guiding the movement of the carrier 20, a carrier driving part 21 (FIG. 2) moving the carrier 20 right and left along the carrier shaft 50, and a feed roller driving part 61 driving a feed roller 60 to transport a sheet of paper to be printed, as shown in FIG. 1.
The carrier 20 is provided with a guide slider 29 formed at a rear side of an upper part thereof to be movable right and left coming in contact with a vertical wall 11′ of the guide rail 11, and a supporting bracket 26 receiving the carrier shaft 50 and supported on the carrier shaft 50 to be movable right and left thereon.
As shown in FIG. 2, the carrier driving part 21 is composed of a carrier driving motor 28 fixed on a rear frame 15 of the chassis 10, and a carrier transfer belt 23 connected with a driving pulley 24 of the carrier driving motor 28. The carrier transfer belt 23 transmits a driving force of the carrier driving motor 28 to a power-transmitting saw tooth 25 formed at the rear side of the carrier 20 to move the carrier 20 right and left.
The feed roller driving part 61 has a feed roller driving motor 62 fixed at a lower part of the side frame 12, a power-transmitting pulley 66 connected to a driving pulley 63 of the feed roller driving motor 62 through a power-transmitting belt 65 and having a power-transmitting gear 67, and a feed roller driving gear 69 engaged with the power-transmitting gear 67.
The operation of the inkjet printer 1 constructed as above will be described.
When a printing command is issued from a computer or a controller, the feed roller driving motor 62 drives a pickup roller (not shown) connected to the feed roller driving gear 69 of the feed roller driving part 61 through a separate gear train (not shown) to pickup a sheet of paper from a paper cassette or tray (not shown) and transport it toward the feed roller 60.
After arriving at the feed roller 60, the sheet of paper is transported toward the print head 30 in a predetermined feed rate by the feed roller 60 connected with the feed roller driving gear 69 through the power-transmitting belt 65 transmitting the driving force of the feed roller driving motor 62, the power-transmitting pulley 66, and the power-transmitting gear 67.
Thereafter, when the sheet of paper passes below the print head 30, the print head 30 jets ink through the nozzle onto the sheet of paper, moving left and right along the guide rail 11 and the carrier shaft 50 by the carrier 20 which is moved left and right through the driving pulley 24 transmitting the driving force of the carrier driving motor 28, the carrier transfer belt 23, the power-transmitting saw tooth 25, et al.
Thus, to move the carrier 20 mounting the print head 30 thereon during printing, the conventional inkjet printer 1 uses the carrier transfer belt 23, which is connected to the driving pulley 24 of the carrier driving motor 28 to transmit the driving force of the carrier driving motor 28 to the power-transmitting saw tooth 25 of the carrier 20.
But to stably transmit the driving force of the carrier driving motor 28 from the driving pulley 24 to the power-transmitting saw tooth 25 of the carrier 20, the carrier transfer belt 23 should be maintained in a tensioned state.
To accomplish this, in the conventional inkjet printer 1, as shown in FIGS. 3 and 4, a pulley fixing apparatus 70 is installed at a driven pulley 78 on the opposite side of the driving pulley 24 to adjust a tension of the carrier transfer belt 23.
The pulley fixing apparatus 70 is provided with a pulley cap 71, a bracket 75, and an adjusting part 72, 80 moving the pulley cap 71 in a longitudinal direction of the carrier transfer belt 23. The pulley cap 71 has support holes 74 rotatably receiving a shaft 79 formed to protrude from both sides of the driven pulley 78. The bracket 75 is located at the rear frame 15 to movably support the pulley cap 71 by receiving guides 73 formed at upper and lower walls of the pulley cap 71 through guide holes 76.
The adjusting part 72, 80 is composed of a female screw 72 that protrudes from a vertical wall of the pulley cap 71, and a tension adjusting screw 80 combined with the female screw 72 through a threaded hole 77 on the bracket 75, and an E-shaped ring 83, an O-shaped ring 82, and a spring 81, which are disposed in the inside of the bracket 75.
The conventional pulley fixing apparatus 70 constructed as above can relatively easily control the tension of the carrier transfer belt 23, since it adjusts a distance between the driving pulley 24 and the driven pulley 78 by rotating the tension adjusting screw 80 combined with the female screw 72. But to install the carrier transfer belt 23 and the driven pulley 78, complicated and troublesome assembling operations are required to combine the driven pulley 78 with the pulley cap 71, and then fix the pulley cap 71 to the bracket 75 by the tension adjusting screw 80.
Also, since the conventional pulley fixing apparatus 70 uses a large number of parts, manufacturing cost is increased.